low brightness problem in Ge Force 8400M GS graphic problem

i bought a second hand laptop.its hp pavilion hp dv6500.
it has AMD processor ATHLON and in it there is a NVIDIA GRAPHIC CARD Ge Force 8400M GS

its brightness is too low

i can decrease its brightness and can increase up to certain limit.still its dim.

how to increase my brightness??

is there any compatibility issue???

i hope u will respond